Combustion Characteristics of Premixed Hydrogen/Air in an Undulate Microchannel

Abstract

This work reports a numerical investigation of microcombustion in an undulate microchannel, using premixed hydrogen and air to understand the effect of the burner design on the flame in order to obtain stability of the flame. The simulations were performed for a fixed equivalence ratio and a hyperbolic temperature profile imposed at the microchannel walls in order to mimic the heat external losses occurred in experimental setups. Due to the complexity of the flow dynamics combined with the combustion behavior, the present study focuses on understanding the effect of the fuel inlet rate on the flame characteristics, keeping other parameters constant. The results presented stable flame structure regardless of the inlet velocity for this type of design, meaning that a significant reduction in the heat flux losses through the walls occurred, allowing the design of new simpler systems. The increase in inlet velocity increased the flame extension, with the flame being stretched along the microchannel. For higher velocities, flame separation was observed, with two detected different combustion zones, and the temperature profiles along the burner centerline presented a non-monotonic decrease due to the dynamics of the vortices observed in the convex regions of the undulated geometry walls. The geometry effects on the flame structure, flow field, thermal evolution and species distribution for different inlet velocities are reported and discussed.

A Review on Micro-Combustion Flame Dynamics and Micro-Propulsion Systems

“…PFB, though initially observed without distinction from FREI, was first identified in the course of micropropulsion studies conducted with wavy geometries [81,82], involving various inlet velocities and equivalence ratios, using a mixture of H 2 and air. The geometry used is similar to our research, and it incorporated different wall conditions (hyperbolic and linear temperature profiles, as well as adiabatic conditions).…”

“…In a recent study by Resende et al [82], flame dynamics within a wave-shaped combustor featuring substantial divergence and convergence variations were investigated. The study employed a hydrogen/air mixture and revealed a pronounced interaction between fluid dynamics and chemical reactions.…”

An Investigation into Burner Configuration Effects on Premixed Flame Characteristics for LPG Diluted with CO₂

“…al. [19], reported the influence of flame and flame stability by the design of the burner through a numerical simulation for the combustion of premixed hydrogen/air in an undulate microchannel. As flow dynamics and combustion behavior are so complicated, only the effect of the fuel inlet rate on the flame characteristics have been taken into account, keeping other variables the same.…”